Vertical axis wind turbines can be divided into two general types, savonius turbines and darrieus turbines. Darrieus turbines tend to have a plurality of symmetrical air foils that have a zero rigging angle, that is, the angle that the air foils are set relative to the structure on which they are mounted. Savonius turbines, when looking down on the rotor from above, having an S-shape in cross section, if it was of the two-blade variety.
Savonius turbines are considered to be of the drag-type of device and are used whenever cost or reliability is more important than efficiency.
Having a helix shaped vertical axis wind turbine blade provides a surface that will “catch” the wind from differing directions. The placement of dual helix shaped blades 180 degrees apart or triple helical shaped blades 120 degrees apart or quadruple helical blades 90 degrees apart provide for a reliable turbine configuration that aids in providing turbine rotation for just about any direction of wind passing thereby.
Prior known vertical axis helically shaped blades have been built and constructed in a segmented faction because the outer curved edge area of a helically constructed turbine blade has a larger surface than the area thereof adjacent a vertical axis of each blade. As a result, the prior art discloses a plurality of segmented curved end blades that are stacked upon one another to provide an approximation of a helical shaped blade, as shown in U.S. Pat. No. 7,364,406.
When a larger helically configured sheet is utilized in a vertical axis wind turbine, such as shown in advertising for Alternative Power Turbines Gale R15 series, the outer edge of each turbine blade is not vertically oriented as it is not parallel to the vertical axis of the turbine blade because of the extra surface area needed toward the outer edge of each blade.
Another helical shaped vertical axis wind turbine is shown at U.S. Pat. No. 7,494,315 which by its nature is cut into a large single segment, specifically constructed for the height and width of the turbine blade.
A need has developed for helical shaped vertical axis turbine blades that are formed inexpensively from sheet material in a somewhat continuous manner so that helical blades of differing lengths or heights can be constructed as desired and approximately continuously formed to be cut at such desired lengths.
It is, therefore, an object of the invention, generally stated, to provide a new and improved vertical axis helical type curved shaped turbine blade and an improved method for continuous manufacturing the blades.